1. Field of the invention
The present invention relates to a flat-plate antenna for installation in an electrical apparatus such as a portable terminal or an electric appliance or on a wall or the like, and method for manufacturing the same, and more specifically, to flat-plate antenna and method for manufacturing the same for realizing thinner shape and excellent productivity, reducing labor for installation in an electrical apparatus or on a wall, and exhibiting desired antenna characteristics stably.
2. Prior Art
In recent years, except large-scale antennas for use in base station or satellite broadcasting, tendency to compactness of various kinds of antennas for use in a potable telephone or a mobile computer (hereinafter collectively referred to as “a portable terminal”) have been progressing. Especially, accompanied with tendency to compactness of portable terminal itself, an antenna for use in a portable terminal is required to solve problems of installation space and request for satisfying characteristics contradicting to restriction of antenna volume. Moreover, in a plan of domestic wireless network which has been progressing recently, problem of an antenna size has been arisen, in accordance with installation of an antenna in a personal computer or an electric appliance (hereinafter collectively referred to as “an electric appliance”) or on a wall surface within a room.
In FIG. 1(a) and FIG. 1(b), an example of a conventional small-size antenna is shown. This small-size antenna is a kind of inverted-F antenna, and is formed by connecting a chip antenna 50 on a ground portion 53 of a copper plate by solder reflowing. The chip antenna 50 having a radiating element portion 51a, 51b, a connecting portion 51c and a power supply portion (not shown in the figure) each of which are formed by covering a surface of a ceramic dielectric 52 with a cupper layer by photolithography,. The construction as described above leads to shorten length of a radiating element portion 51a of an antenna due to dielectric constant of a ceramic dielectric exceeding ten (10). Consequently, compact and lightweight antenna is realized.
However, according to a conventional small-size antenna, firstly, antenna efficiency is inferior due to large dielectric loss of a ceramic dielectric. Secondly, tendency to compactness and lightweight of a potable terminal such as a note-type personal computer or a potable telephone may be obstructed due to restriction of antenna thickness due to dependence of overall antenna thickness on a ceramic dielectric thickness. Thirdly, labor for connecting a power supply line is needed during installation work of an antenna in an electrical apparatus or on a wall. Fourthly, productivity of an antenna is inferior because process for forming a cupper layer on a radiating element potion and process for connecting a chip antenna on a cupper plate are separate. Fifthly, cost of an antenna increases due to inferior productivity of an antenna and expensiveness of a ceramic dielectric.